metro_data = [
    ('Tokyo', 'JP', 36.933, (35.689722, 139.691667)),
    ('Delhi NCR', 'IN', 21.935, (28.613889, 77.208889)),
    ('Mexico City', 'MX', 20.142, (19.433333, -99.133333)),
    ('New York-Newark', 'US', 20.104, (40.808611, -74.020386)),
    ('Sao Paulo', 'BR', 19.649, (-23.547778, -46.635833)),
]

#下面的代码要对其按国家代码来排序
def action():
    from operator import itemgetter
    return sorted(metro_data, key=itemgetter(1))

def test_action():
    assert action() == [('Sao Paulo', 'BR', 19.649, (-23.547778, -46.635833)), ('Delhi NCR', 'IN', 21.935, (28.613889, 77.208889)), ('Tokyo', 'JP', 36.933, (35.689722, 139.691667)), ('Mexico City', 'MX', 20.142, (19.433333, -99.133333)), ('New York-Newark', 'US', 20.104, (40.808611, -74.020386))]
